18.3.1: Diagnostic methods and cycle manipulation in the mare

Question 1

True/false: a mare in the transitional period may stand to be bred/ appear to be in oestrus.

Answer 1

True

Question 2

In late autumn, the mare’s cyclicity often ends with…

Answer 2

A silent or anovulatory heat

Some ponies cycle throughout the winter.

Question 3

What are signs of the transitional period?

Answer 3

• Mare may show oestrus behaviour
• Mare may stand to be bred
• Mare has follicles that grow and regress (not enough LH or LH-receptors) but these do not ovulate
• Ovaries may be large with palpable follicles

Question 4

The breeding season starts ~15th Feb so shortening the transitional period is necessary. How can this be achieved?

Answer 4

• Providing 16hrs artificial light and additional nutrition from 1st Dec
• (Some clinicians also administer GnRH at this time; efficacy unproven)
• Once the mare is in the transitional period (follicles greater than 25mm in diameter) -> progestogens are administered to suppress the release of LH
• This is in the form of altrenogest (Regumate) given in feed for ~10 days
• Follicles grow during progestogen treatment
• When follicles reach 45mm progestogen treatment is stopped and there is a release of LH which induces ovulation
• (Some clinicians also give GnRH at this time to enhance the LH surge)

Question 5

What 3 things can we used the manipulate the transitional phase?

Answer 5

• Light
• Progesterone/ progestogens
• GnRH

Question 6

What can we use to hasten ovulation in mares that are in oestrus?

Answer 6

• GnRH
• hCG (this is LH-like in activity)

Question 7

When it the optimal mating time in mares?

Answer 7

• Optimum mating = 24-48hrs before ovulation -> this means the sperm is in the tract waiting for the egg
• Mares ovulate a secondary oocyte that is immediately fertilisable but remains viable for only 12hrs after ovulation

Question 8

Signs of approaching ovulation on ultrasound

Answer 8

• Follicle size (~40-50mm)
• Follicle softening
• Follicle wall thickened
• Follicle haemorrhage
• Follicle pointing
• Reduction in uterine oedema

Question 9

What can we use to induce return to oestrus when the mare is cycling but in the luteal phase?

Answer 9

Prostaglandin

Question 10

Describe the characteristics of repro tract when the mare is in anoestrus

Answer 10

Anoestrus
* Ovaries: small and hard, with small follicles
* Uterus: flaccid
* Vagina: pale and dry
* Cervix: small and closed

Question 11

Describe the characteristics of the repro tract when the mare is in the transitional phase

Answer 11

Transitional phase: irregular cycles, long oestrus
* Ovaries: larger - soft follicles that grow and regress
* Uterus: transitional
* Vagina: like anoestrus
* Cervix: like oestrus

Question 12

Describe the characteristics of the repro tract when the mare is in oestrus

Answer 12

Oestrus
* Ovaries: medium with either follicle or corpus haemorrhagicum present
* Uterus: large and oedematous
* Vagina: moist and hyperaemic
* Cervix: broad and soft

Question 13

Describe the characteristics of the repro tract when the mare is in dioestrus

Answer 13

Dioestrus
* Ovaries: medium sized, early CH feels like follicle. CL not palpable.
* Uterus: small and tonic
* Vagina: pale and dry
* Cervix: hard and narrow

Question 14

Describe the characteristics of the repro tract when the mare is pregnant

Answer 14

Pregnant
* Ovaries: early on, these are medium-sized, but become very large when eCG is secreted
* Uterus: tonic and pregnancy swelling can be detected from 21 days
* Vagina: pale and dry
* Cervix: hard and narrow

Question 15

What bacterial venereal pathogens do you screen for in the mare? What disease do these organisms cause?

Answer 15

• Taylorella equigenitalis
• Klebsiella pneumoniae
• Pseudomonas aeruginosa

These organisms cause contagious equine metritis -> the mare does not get pregnant. They do not cause late abortion.

Question 16

You have taken a clitoral sinus and clitoral fossa swab and want to test for Taylorella - what transport do you use and why? When must your sample reach the lab?

Answer 16

• Taylorella is microaerophilic so has to be held at low oxygen -> transport in charcoal
• Must arrive at lab promptly - do not swab on Friday or Saturday, do not want to get stuck in post

Question 17

What should you do if CEM is isolated in mares prior to covering?

Answer 17

• Isolate and treat infected mares
• Notify owners of mares

Question 18

What should you do if CEM is isolated in stallions prior to covering?

Answer 18

• Isolate and treat stallions
• Notify owners of mares that covering may not be taking place as planned

Question 19

What should you do if CEM is isolated in mares and stallions after covering?

Answer 19

• Cease covering
• Check all mares implicated in the outbreak
• Do not cover until 3 negative swabs each at least 2 days apart

Question 20

What viral venereal pathogens do we screen for in mares?

Answer 20

• Ensure the mare is serologically negative to Equine Viral Arteritis (EVA)

Question 21

How is Equine Viral Arteritis transmitted?

Answer 21

• Via respiratory tract route
• Venereally including in chilled semen

Question 22

Clinical signs of Equine Viral Arteritis

Answer 22

• Flu-like with significant conjunctivitis (pink eye), focal dermatitis, limb and ventral oedema
• Pregnant mares may abort
• Aborted foetuses appear partially autolysed (compared to fresh foetus in EHV) but still need appropriate pathological exam and testing

Question 23

Which animals can become persistently infected with Equine Viral Arteritis?

Answer 23

• When stallions are infected with EVA, it can infected the accessory glands and result in persistent infection
• Mares clear the infection within 1 month and develop immunity

Question 24

True/false: Equine Infectious Anaemia is notifiable.

Answer 24

True

Question 25

What non-venereal pathogens might we screen/ plan for in an animal coming to stud?

Answer 25

* **Equine herpes virus 1** -> plan vaccination for months 5, 7 and 9 of pregnancy * **Equine herpes virus 3 (equine coital exanthema)** - inspect and ensure negative * **Equine infectious anaemia (EIA)** -> ensure horses returning to the UK are serologically negative * **Strangles** - quarantine on entry to demonstrate no signs develop

Question 26

When would you take uterine swabs in the mare?

Answer 26

* For bacterial venereal pathogen screening * In cases of endometritis * For endometrial bacteriology (in endometritis) to allow C&S * For the detection of other pathogens e.g. yeast, fungi

Question 27

When would you **not** expect to find bacteria in the uterus?

Answer 27

* In the luteal phase - the cervix is closed so this would be significant if found * However uterine swabs are often taken during oestrus (HBLB guidance) when the cervix is open and you might find bacteria

Question 28

If a mare has a Category I endometrial biopsy, what does this mean for her estimated foaling rate? What about a Category III mare?

Answer 28

**Endometrial biopsies** * Category I - no pathological changes and should have normal fertility; estimated foaling rate 80-90% * Category III - severe endometrial changes; uterus may be incapable of supporting foetal development. Estimated foaling rate <10%

Question 29

What term is given to this phase?

Answer 29

Transitional phase

Question 30

What phase of her cycle is this mare in?

Answer 30

**Oestrus**

Question 31

Answer 31

Large volume of uterine fluid in a pyometra

Question 32

Answer 32

Typical appearance of a mare CL

Question 33

Answer 33

Abnormal CL with honeycomb appearance: This is an anovulatory luteinised/ haemorrhagic follicle commonly seen at the end of the breeding season in older mares

Question 34

This mare has been barren for more than 2 seasons. She was served at a professional stud with appropriate veterinary management. She presents with fluid in her uterus shown below. What conclusions can you make about the likelihood of getting her pregnant?

Answer 34

* This mare has long-term fluid accumulation in the uterus typical of chronic endometritis -> she has got chronic endometrial disease * She will have a poor prognosis for getting pregnant * She will have a poor prognosis for taking a foal to term * Attempting to manage this mare will cost a lot of money

Question 35

You are examining endometrial cytology from a mare. How many neutrophils is too many neutrophils to be normal?

Answer 35

Question 36

Indications for taking an endometrial biopsy

Answer 36

* Barren mares * Repeat breeeder mares * Mares with early embryonic death or abortion * Anoestrus mares (during breeding season) * Mares requiring surgery of genital tract * Pyometra or mucometra * Fertility evaluation pre-purchase **Endometrial biopsies can inform you of the chances of a mare taking a foal to term.**

Question 37

When can you take an endometrial biopsy?

Answer 37

* **Mid-dioestrus** = good time as it minimises misleading histological changes * Biopsy can be taken at any time except pregnancy or when fibrosis of the cervix prevents it

Question 38

Answer 38

Normal endometrium

Question 39

Answer 39

Uterine adhesion

Question 40

Answer 40

Endometrial cyst

Question 41

Answer 41

This is **Equine coital exathema** * Do not breed this mare until the lesions have resolved * Check for lesions on the stallion's penis * Remember the mare may have been cleaned/ tail bandaged etc. by a member of staff with contaminated hands/ equipment

Question 42

What are the consequences of equine coital exathema?

Answer 42

* Does not result in abortion or infertility * Stallion may be sore and unwilling to breed